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So this was a patient that presented with

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left brachial plexus dysfunction, and

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that was the actual history on this case.

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And the patient underwent a pre- and

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post-contrast MRI of the brachial plexus.

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So, on the left-hand side is

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a coronal STIR-weighted image.

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And when we look at the coronal STIR-weighted

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image, what we see is this mass right

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here involving the left axillary region.

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Now, a couple of things on this case is this

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is actually below the level of the clavicle.

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So this is in the infraclavicular area.

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So we see a mass right here involved in

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the axillary area, so we know it's abnormal.

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But the next thing is that we have to

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identify is what is it actually arising from?

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Could this be a lymph node?

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Could it be something arising

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from the brachial plexus?

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Could it be arising from the chest wall?

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Et cetera.

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The middle image here

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demonstrates the mass right here.

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And we can see on this contrast-enhanced

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T1-weighted image that the mass is pretty

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well-rounded, has nice, clear margins,

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not really infiltrating the adjacent fat.

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But, it's in very close proximity to this

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vessel right here, and that little vessel

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right here is the subclavian artery.

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So it's adjacent to the subclavian artery,

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and if you look real closely, we can see two

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other dots right here, and those two other

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dots are the cords of the brachial plexus.

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So all of a sudden right now, we're thinking

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that there's a mass that's in very close

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relationship to the subclavian artery.

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Then what we can do is then look at the

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coronal non-contrast T1-weighted image.

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And when we look at the coronal non-

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contrast T1-weighted image, remember

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the principles of the brachial plexus.

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So we have a mass that's

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located below the clavicle.

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So here's the clavicle here.

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So this is in the infraclavicular region.

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We know that it's lateral to the chest wall,

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so it's not infiltrating the chest wall.

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And now we start seeing our

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anatomic friend right here.

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And this anatomic friend right

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here is the subclavian artery.

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So when we look at the subclavian artery,

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the next thing that we have to start to look

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for are the cords of the brachial plexus.

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So we can see one cord that's superior

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to it, but we can see another cord

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right here that's inferior to it.

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And we can see how this cord is directly

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extending into this mass right here.

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So when we put this all together,

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the well-defined mass that's

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homogeneously enhancing this thing.

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that's adjacent to the subclavian artery,

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and our coronal images actually show

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this mass in complete continuity with

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the cords of the brachial plexus, we can

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make the diagnosis of a neurogenic tumor.

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In this case, this was a schwannoma involving the

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brachial plexus that was in the infraclavicular

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component of the brachial plexus.